Currently it is not possible to create a fully optical communication system without a software tool which simulates an optical communication line in real conditions prior to its construction. The aim of this article is to establish a comparison between the EDFA (erbium doped fibre amplifier) and SOA (semiconductor optical amplifier) optical amplifiers in the WDM (wavelength division multiplexing) system. The system contains a four-channel WDM with speed of 10 Gbps and optical fibre with length of 80 km. Simulations are conducted in the programme environment “OptSim.” The quality of the optical communication system is evaluated by the BER (bit error rate) and Q-factor for individual wavelengths, namely, of 1558 nm and 1562 nm, which are within the C-band.

The aim of this article is to demonstrate change in the BER (Bit Error Rate) and Q-factor in long distance lines. Nowadays it is not possible to create fully optical communication systems without software tools to simulate real optical networks under the given circumstances. There have been two 10 Gbps optical line topologies created: one without EDFA (Erbium Doped Fibre Amplifier) of up to 115 km and another using EDFA on a long distance line up to 3200 km. The article shows the BER worsening with the distance increasing and also the need for the link amplifier.

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<div>This article is devoted to the problematic of error rate and modulations in optical communication. Optic waveguide shows insufficiencies in high speed transfers manifested by corrupted transfer. Although modern technological processes contributed to lowering these insufficiencies, it would be uneconomical to completely reconstruct the optical network infrastructure. The solution is only partial so we approach more economical methods, such as modulations. The article works with a 10 Gbps channel with two modulation types, namely DPSK (Differential Phase Shift Keyed) and RZ-DPSK (Return to Zero-Differential Phase Shift Keyed). These modulations are evaluated and compared according to BER (Bit Error Rate) and Q-factor.<div> </div></div>